This research is directed towards the genetic and biochemical characterization of lambda DNA replication. Attempts are being made to identify phage and bacterial genes and their products involved in the very early events of lambda replication. Lambda DNA circles in lysogens undergo two nicking processes following inactivation of lambda repressor. Genetic and biochemical data suggest that one type of nick is membrane-associated. Attempts are being made to determine if membrane-associated nicking is strand and site specific. Some chemical and physical agents that produce alterations in the membrane also result in repair of these nicks. We are studying this phenomenon further through mutational, chemical and biological means.